1. Field of the Invention
The present invention relates generally to a tone detector and particularly to a tone detector capable of accurately detecting tone signals in a short period of time.
2. Description of the Related Art
In a communication apparatus such as the facsimile machine, tone signals need to be detected in order to perform communication such as data transmission/reception. In the following, a description of the conventional tone signal detection method is given with reference to FIG. 1.
FIG. 1 is a schematic diagram illustrating the measuring time for identifying the tone signal according to the conventional art. The tone signals are measured in each fixed time period T into which the measuring time is divided as indicated in the drawing, and the type of tone signal is determined in each time period T based on the above measuring results.
However, the above tone signal detection method is time consuming since it requires time T to measure the tone signal.
On the other hand, if the measuring time T is shortened in order to speed up the tone signal detection, an accurate measurement cannot be made. Thus, in the conventional art, it has been impossible to accurately identify a tone signal in a short measuring time period.